Arducopter 2.9.1 Rc1 released

[Jumpy07]

http://code.google.com/p/arducopter/downloads/detail?name=ArduCopter-2.9.1-rc1.zip&can=2&q=

ArduCopter 2.9.1-rc1 (release candidate #1) for beta testers only!

Improvements over 2.9 are:
1) THR_MID parameter added to allow users to adjust the manual throttle so that vehicle hovers at about mid stick
2) bug fix for autotrim - roll axis was backwards
3) bug fix to set sonar_alt_health to zero when sonar is disabled
4) capture level roll and pitch trims as part of accel calibration
5) bug fix to ppm encoder false positives